In recent years, it has been reported that iPS cells are established by introduction of reprogramming-inducing genes into human skin-derived fibroblasts (WO 2007/069666 A1, Takahashi, K. et al., Cell, 131: 861-872 (2007), WO 2008/118820 A2 and Yu, J. et al., Science, 318: 1917-1920 (2007)). Since the iPS cells can be made to differentiate into cells of various tissues after being established from cells derived from the patient to be treated, they are expected to be useful as a graft material which does not cause the rejection reaction.
However, it was reported that, after inducing differentiation into neural progenitor cells, some mouse iPS cells remain undifferentiated and cause tumor formation when they are transplanted into mice (Miura K. et al., Nat Biotechnol., 27: 743-745 (2009)). Such remaining of undifferentiated cells is considered to be due to properties of individual iPS cell lines. Further, since many cell lines are established at once by the process of establishing iPS cells, a simple method for selecting iPS cell lines suitable for transplantation among many iPS cell lines has been demanded.